Messages in this thread Patch in this message | | | From | Asahi Lina <> | Date | Fri, 24 Feb 2023 19:53:17 +0900 | Subject | [PATCH 5/5] rust: device: Add a stub abstraction for devices |
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From: Wedson Almeida Filho <wedsonaf@gmail.com>
Add a Device type which represents an owned reference to a generic struct device. This minimal implementation just handles reference counting and allows the user to get the device name.
Lina: Rewrote commit message, dropped the Amba bits, and squashed in simple changes to the core Device code from latter commits in rust-for-linux/rust. Also include the rust_helper_dev_get_drvdata helper which will be needed by consumers later on anyway.
Co-developed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Signed-off-by: Asahi Lina <lina@asahilina.net> --- rust/helpers.c | 13 +++++++++ rust/kernel/device.rs | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++- 2 files changed, 88 insertions(+), 1 deletion(-)
diff --git a/rust/helpers.c b/rust/helpers.c index 04b9be46e887..54954fd80c77 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -20,6 +20,7 @@ #include <linux/bug.h> #include <linux/build_bug.h> +#include <linux/device.h> #include <linux/err.h> #include <linux/refcount.h> @@ -65,6 +66,18 @@ long rust_helper_PTR_ERR(__force const void *ptr) } EXPORT_SYMBOL_GPL(rust_helper_PTR_ERR); +void *rust_helper_dev_get_drvdata(struct device *dev) +{ + return dev_get_drvdata(dev); +} +EXPORT_SYMBOL_GPL(rust_helper_dev_get_drvdata); + +const char *rust_helper_dev_name(const struct device *dev) +{ + return dev_name(dev); +} +EXPORT_SYMBOL_GPL(rust_helper_dev_name); + /* * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type * as the Rust `usize` type, so we can use it in contexts where Rust diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index 9be021e393ca..e57da622d817 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -4,7 +4,7 @@ //! //! C header: [`include/linux/device.h`](../../../../include/linux/device.h) -use crate::bindings; +use crate::{bindings, str::CStr}; /// A raw device. /// @@ -20,4 +20,78 @@ use crate::bindings; pub unsafe trait RawDevice { /// Returns the raw `struct device` related to `self`. fn raw_device(&self) -> *mut bindings::device; + + /// Returns the name of the device. + fn name(&self) -> &CStr { + let ptr = self.raw_device(); + + // SAFETY: `ptr` is valid because `self` keeps it alive. + let name = unsafe { bindings::dev_name(ptr) }; + + // SAFETY: The name of the device remains valid while it is alive (because the device is + // never renamed, per the safety requirement of this trait). This is guaranteed to be the + // case because the reference to `self` outlives the one of the returned `CStr` (enforced + // by the compiler because of their lifetimes). + unsafe { CStr::from_char_ptr(name) } + } +} + +/// A ref-counted device. +/// +/// # Invariants +/// +/// `ptr` is valid, non-null, and has a non-zero reference count. One of the references is owned by +/// `self`, and will be decremented when `self` is dropped. +pub struct Device { + pub(crate) ptr: *mut bindings::device, +} + +// SAFETY: `Device` only holds a pointer to a C device, which is safe to be used from any thread. +unsafe impl Send for Device {} + +// SAFETY: `Device` only holds a pointer to a C device, references to which are safe to be used +// from any thread. +unsafe impl Sync for Device {} + +impl Device { + /// Creates a new device instance. + /// + /// # Safety + /// + /// Callers must ensure that `ptr` is valid, non-null, and has a non-zero reference count. + pub unsafe fn new(ptr: *mut bindings::device) -> Self { + // SAFETY: By the safety requirements, ptr is valid and its refcounted will be incremented. + unsafe { bindings::get_device(ptr) }; + // INVARIANT: The safety requirements satisfy all but one invariant, which is that `self` + // owns a reference. This is satisfied by the call to `get_device` above. + Self { ptr } + } + + /// Creates a new device instance from an existing [`RawDevice`] instance. + pub fn from_dev(dev: &dyn RawDevice) -> Self { + // SAFETY: The requirements are satisfied by the existence of `RawDevice` and its safety + // requirements. + unsafe { Self::new(dev.raw_device()) } + } +} + +// SAFETY: The device returned by `raw_device` is the one for which we hold a reference. +unsafe impl RawDevice for Device { + fn raw_device(&self) -> *mut bindings::device { + self.ptr + } +} + +impl Drop for Device { + fn drop(&mut self) { + // SAFETY: By the type invariants, we know that `self` owns a reference, so it is safe to + // relinquish it now. + unsafe { bindings::put_device(self.ptr) }; + } +} + +impl Clone for Device { + fn clone(&self) -> Self { + Device::from_dev(self) + } } -- 2.35.1
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